1. Field of the Invention
The present invention relates to a peristaltic pump suitable for use in, for example, transfusion.
2. Prior Art
Hitherto, various peristaltic pumps have been proposed as disclosed, for example, in Japanese Unexamined Patent Publication No. 56-113084. In general, a known peristaltic pump has a plurality of cams, a plurality of pressing fingers actuated by the cams so as to move between a retracted position and an operative position, and a platen opposing the pressing fingers so as to carry a tube therebetween. In operation, the pressing fingers are successively actuated to the operative position by the cams so as to collapse the tube, whereby a liquid in the tube is displaced and transported, while the elastic tube is allowed to restore when relieved from the pressing force so as to expand the liquid passage, thus performing a pumping action.
In the peristaltic pump of the type described, problems are caused such as damaging of the tube due to excessive pressing, unduly large load posed on the cam actuating device, and so forth, as a result of any dimensional errors caused during manufacture of the components such as the cams, pressing fingers and the platen, as well as insufficiency in the locating precision of these components. In order to obviate these problems, it has been proposed to provide an elastic support member on the back side of the platen opposite to the pressing fingers, so that any excessively large pressing force is absorbed by the elastic deformation of the supporting member thereby relieving and unburdening the platen.
When the platen is unburdened, the pressing force to be relieved acts only on a local point on the tube which is immediately under a certain pressing finger which has been set to the operative position. Therefore, during the unburdening, the platen does not always make a translational movement. Namely, the platen may be moved at an inclination with respect to the plane of the group of pressing fingers. In such a case, the support of the tube on the platen is rendered unstable so as to impair the precision in control of the flow rate of the liquid during transfusion.
Under this circumstance, Japanese Unexamined Utility Model Publication No. 62-20182 discloses a peristaltic pump which is improved to eliminate the above-described problems concerning unburdening of the platen. In this improved peristaltic pump, any excessive force which would unduly collapse the tube is relieved not by a displacement of the platen but by elastic deformation of an elastic buffering portion of each pressing finger made of an elastic material. Thus, any excessive force applied to a pressing finger, which would otherwise be exerted on the tube, is effectively absorbed by the pressing finger itself.